Safety device for roller mills



April 19, 193$. THALMANN 2,114,660

SAFETY DEVICE FOR ROLLER MILLS Filed 001.6, 1936 Patented Apr. 19, 1938UNITED STATES PATENT OFFICE Emil Thalmann, Niederuzwil, Switzerland,assignor to firm Gebriidcr Biihler, Uzwil, Switzerland ApplicationOctober 6,

2 Claims.

the rollers, particularly the axle pins of the same I and the correlatedbearings, are heavily strained, thus inviting damage. In order toprotect the machine against damage, when subjected to such heavystraining, it is known, to apply safety elements such as may be termeddisruptive bolts.

According to the present invention an improved safety device againstdamaging of the mill, due to the grinding pressure exceeding apredetermined value, is provided which comprises a bolt-like disruptiveelement anchoring a tension ing rod for adjusting the grinding pressureto an abutment of the mill frame, the element being removably connectedto said rod and having a neck portion of a smaller cross section thanthat of its "portion connecting with the rod which neck portion isdisposed between said connecting portion and a head on the element bymeans of which the latter is anchored to said abutment, so as to failincidental to excessive grinding pressure arising.

This arrangement permits of providing a compact rigid construction forthe disruptive ele-v ment and of transmitting the tension developing inthe tensioning rod during the operation of the mill to the element freefrom secondary strains. In this Way is ensured that the disruptiveelement breaks with certainty only when the grinding pressure exceeds apredetermined value, in distinction from safety devices in which thedisruptive element is subjected to secondary straining in addition tothe direct tensile strain accruing from the grinding pressure.

In the accompanying drawing the invention is illustrated as applied byway of example to a roller mill only the parts of which necessary for aproper understanding of the invention are shown. In this drawing Fig. 1shows a fragmentary sectional end elevation of the roller mill on theline II in Fig. 2, with the drive box cover removed;

Fig. 2 shows a sectional plan view of Fig. l on the line IIII in thelatter, and

1938, Serial No. 104,293

Fig. 3 is a sectional View of a detail of Fig. l. on a larger scale.

In the drawing, numeral i designates one of the bearings of a grindingroller i3 of the mill to be protected by the safety device and numeral 2designates a pivot by means of which this bearing is rockably arrangedon the frame A of the mill. The tensioning rod 3 of the grindingpressure adjusting arrangement of the mill is anchored to the mill frameA by means of a disruptive bolt 4 which is screwed in the outer end ofsaid rod and the other end of the rod is rotatably connected to a lugii! on a projection of the pivotal bearing l. The tensioning rod 3 ismounted in a sleeve 5 which in turn is screwed in an interior screwthread 6 on a spherical mounting member S which connects with the millframe A in the manner of a universal joint by engaging into matingdepressions in a bore H of this frame. On the outer end of the sleeve 5,which is splined to the rod 3, a hand wheel I of suitable constructionis arranged for controlling the axial displacements of the sleeve 5 inthe screw thread 6, while the rod rotates together with the sleeve. Aterminal cap i2 is screwed on this sleeve end, adjacent to the wheel forclosing the sleeve and thereby holding the head of the disruptive boltin position by the inside of the cap bearing against the outer end ofthe bolt. The underside of the bolt head abuts against a terminalshoulder on the sleeve 5, i. e., the outer sleeve end, in which way theanchorage of the tensioning rod 3 to the mill frame A is effected.

By turning the hand wheel 1, with the .consequent displacements of thesleeve 5 relative to the member 9, the tensioning rod 3 shifts togetherwith the sleeve. The shifting movements of the tensioningrod 3 have theeffect of rocking the bearing i about the pivot 2 in one direction orthe other in which way the pressure between the grinding rollers !3 andM, which. rotate as indicated by the arrow, is regulable, while theuniversal joint prevents secondary bending moments from arising in thetensioning rod 3 in any position of adjustment of the roller i3. Byvirtue of this construction of the safety device the bolt 4 also remainsfree from secondary strains.

When the pressure between the grinding rollers exceeds a predeterminedvalue, the tension in the tensioning rod 3 surpasses a maximum allowablelimit which corresponds to the limit of failure provided for the shortneck portion 8 of the disruptive bolt 4. The smallest crosssection ofthis neck portion is so dimensioned that due to the tensile stressessetting up at this cross section, by transmission of the maximumallowable tension in the rod 3 to the bolt, the

shank and the head of the latter are torn apart.

Due to the fact that the cross section 8 is small as regards the othercross sections of the disruptive bolt 4, the result obtains that at allstrains below the limit of failure the bolt 4 is practically notdeformed. If, however, the strain exceeds the critical limit the head ofthe disruptive bolt is torn off immediately.

Since the screw thread of the disruptive bolt is not overstrained, evenwhen the head of the bolt is torn off, the thread is not injured. Due tothis fact the bolt can be easily removed also in its disrupted conditionfrom the tensioning rod 3, after the cap l2 has been taken ofi, forexample by gripping the projecting end portion of the bolt shank bymeans of a pair of pincers. A fresh disruptive bolt can then readily beinserted, whereupon the cap 12 is screwed in position on the sleeve 5again.

I do not limit myself to the particular size, shape, number orarrangement of parts as shown and described, all of which may be variedwithout going beyond the scope of my invention as shown, described andclaimed.

" What I claim is:

1. In a safety device against damaging of roller mills, due to thegrinding pressure exceeding a predetermined value, cooperating grindingrollers mounted in the mill frame, rockable bearing means for one ofsaid grinding rollers, a mounting sleeve having a detachable bottom, anexterior thread on said sleeve for axially adjustably connecting thesame with said frame, a hand wheel carried by said sleeve forcontrolling the axial adjustments of said sleeve relative to said frame,a tensioning rod for adjusting the grinding pressure splined with itsouter end to said sleeve and rotatably connected at its inner end withsaid rockable bearing means, a bolt-like disruptive element removablyconnected to the outer end of said rod, a head on said element abuttingwith its underside on a terminal shoulder arranged on said sleeve remotefrom said bearing means and with its outer side on said detachablebottom of said sleeve, and a neck portion disposed between said head andthe portion of said element connecting with said rod and having a crosssection smaller than that of said connecting portion so as to fail bytension incidental to excessive grinding pressure setting up. 2. In asafety device against damaging of roller mills, due to the grindingpressure exceeding a predetermined value, cooperating grinding rollersmounted in the mill frame, rockable bearing means for one of saidgrinding rollers, a mounting sleeve, an exterior thread on said sleevefor axially adjustably connecting the same with said frame, a hand wheelcarried on the end of said sleeve remote from said bearing means forcontrolling the axial adjustments of said sleeve in said thread, aterminal screw cap screwed exteriorly on said sleeve adjacent to saidhand wheel, a tensioning rod for adjusting the grinding pressure splinedwith its outer end to said sleeve and rotatably connected at its innerend with said rockable bearing means, a bolt-like disruptive elementremovably connected to the outer end of said rod, in head on saidelement abutting with its underside on a terminal shoulder arranged onsaid sleeve remote from said bearing means and with its outer side onthe inside of said unscrewable cap, and a neck portion disposed betweensaid head and the portion of said element connecting with said rod andhaving a cross section smaller than that of said connecting portion soas to fail by tension incidental to excessive grinding pressure settingup.

EMIL THALMANN.

